And while that may sound far away, in space-terms, that’s spine-chillingly close.

Asteroid 2018 GE3 flew past us today, half the distance to the Moon. Around 50-100 m in diameter, it was several times the 2013 Chelyabinsk meteor, around the size of the 1908 Tunguska event ~ easily enough to destroy a city. We had less than a day’s warning. (📷 Michael Jäger) pic.twitter.com/kElrxBiUoB

A man is sitting on the front porch of a trading post at Vanavara in Siberia. Little does he know, in a few moments, he will be hurled from his chair and the heat will be so intense he will feel as though his shirt is on fire.

That’s how the Tunguska event felt 40 miles [64 kilometres] from ground zero.

It’s not fun to imagine what would have happened if Asteroid 2018 GE3 had found its way to Earth.

“If 2018 GE3 had hit Earth, it would have caused regional, not global, damage, and might have disintegrated in the atmosphere before reaching the ground,” SpaceWeather.com reported.

“Nevertheless, it is a significant asteroid, illustrating how even large space rocks can still take us by surprise. 2018 GE3 was found less than a day before its closest approach.”

Asteroids are small and dark so they are notoriously difficult for scientists to pick up. Plus, they move really quickly, which means a telescope needs to be pointed in just the right spot at just the right time to catch them.